This relates to intravascular heat exchange catheters, and more particularly to heat exchange catheters capable of circulating a heat exchange fluid.
Heat exchange catheters are used in many instances for a variety of reasons. Some surgeries, for example, are better performed when the patient cools to a hypothermic state. In other instances, a patient may suffer from accidental hypothermia and may need to be warmed to a normothermic temperature e.g. 98.6xc2x0 F. Many heat exchange catheters include the capability of infusing fluids such as nutrition, medicine and contrast agents into the blood.
Post surgical patients risk infection and fever. A fever can be controlled through the use of a heat exchange system having an intravascular heat exchange catheter. One such system is disclosed in commonly assigned U.S. Pat. No. 6,146,411. This U.S. Patent is incorporated herein by reference and teaches an exemplary system used to achieve patient normothermia.
The principals of heat exchange applicable to any flowing medium (including blood) dictates the amount of heat transfer. In blood, the heat transferred depends on many things including the volumetric flow rate of the blood, the geometry of the heat exchanger and the temperature difference between the heat exchanger and the blood.
Blood has a maximum desirable heating limit. Beyond about 41xc2x0 C., blood coagulates. This limits the maximum operating temperature of known intravasculature catheters. Because the operating temperature of an intravascular catheter is limited, the catheter geometry takes on an increased importance to effectuate overall heat transfer.
Commonly assigned U.S. Pat. No. 6,126,684, incorporated herein by reference, teaches a heat exchange catheter having smooth tubular balloons in serial alignment to exchange heat with the blood stream of a patient. The balloons each have an exterior surface that facilitates heat exchange with flowing blood.
U.S. Pat. No. 6,096,068 teaches a heat exchange catheter having a contoured outer surface and a heat exchange core. The contoured outer surface increases heat exchange surface area as compared to smooth tubular balloons. The contoured outer surface increases heat exchange fluid turbulence and flowing blood turbulence to improve heat transfer. These effects improve the heat transfer capability of the catheter.
What is desired is a heat exchange catheter with improves geometry to optimize heat transfer between the catheter and flowing blood. What is also desired is a heat exchange catheter that is easily manufactured, and which achieves optimal flexibility.
A intravascular heat exchange catheter includes a catheter body having a proximal end connectable with a heat exchange fluid source and a distal end insertable into the vasculature of a patient to facilitate heat transfer with flowing blood.
The core has at least one heat exchange fluid lumen for circulating heat exchange fluid within the catheter body. A heat exchanger, e.g. a balloon surrounds a portion of the proximal end of the catheter. The heat exchanger is in fluid communication with the heat exchange fluid lumen for enabling heat exchange fluid from the heat exchange fluid source to circulate through the core and the balloon.
A wire, or similar retainer, wraps around the balloon to seal the balloon against the core, forming at least two heat exchange lumens between the balloon and the core. The wire has a helical configuration to seal the balloon against the core along a helical path.
Adhesive, according to one aspect of the invention bonds the balloon to the core along this helical path. According to a variation of the invention, the wire and the adhesive cooperate to maintain the balloon in a helical shape.
Maintaining the balloon in a helical shape can also be accomplished by heat treating the balloon to assume a particular nominal shape having a nominal surface contour. Ideally, the surface contour resembles a helix to enable the wire and/or adhesive to securely mate the balloon to the core without significant elastic resistance caused by balloon deformation.
The core defines a guidewire lumen, which connects with an infusion source for delivering medicine to the vasculature of the patient via the guidewire lumen.